1. Field of the Invention
The present application relates to an anti-ice and de-ice device for structures subject to high strain, and more particularly, to a device for removing ice and preventing ice formation on a rotor blade of a helicopter.
2. Description of Related Art
Aircraft, during flight and/or while on the ground, may encounter atmospheric conditions that cause the formation of ice on airfoils and other surfaces of the aircraft structure, including wings, stabilizers, rudder, ailerons, engine inlets, propellers, fuselage and the like. Accumulation of ice, if not removed, can add excessive weight to the aircraft and alter the airfoil configuration, causing undesirable and/or dangerous flying conditions. General aviation aircraft are particularly susceptible to the detrimental consequences of ice formation because only small amounts of ice on structural members, such as wings, tail, propellers, and the like, can significantly alter flight characteristics.
De-ice and anti-ice devices including resistance heated elements are commonly used to prevent ice formation and remove ice on rotor blades of a helicopter. The resistance heated elements generally consist of wire elements or random carbon mat material. Because fabrication of wire elements is labor intensive, costly, operator sensitive and prone to shorts and electrical failure, the use of a random carbon mat material has typically been used. These resistance heated elements are usually arranged along the span of the blades with return paths for the electrical current so as to return the electrical current from the outboard to the inboard of the blades. The return paths are connected to a power supply, and a feedback control mechanism is used to adjust the electrical current that flows through the resistance heated elements.
Although a random carbon mat material offers uniform heat distribution, pliability, and ease of manufacture, this material is not highly strain tolerant. Therefore, its use in high-strain environment may be of concern. For example, tiltrotor aircrafts have the unique flexibilty to take-off and land like a helicopter, yet cruise at speeds and altitudes like a turbo-prop fixed wing. The Bell V22 aircraft and the Bell Augusta BA 609 aircraft are examples of such tiltrotor aircrafts. These versatile aircrafts use rotor blades that are much thicker than conventional helicopters. As a result, the strain induced by the flapping of the blades is much higher than in conventional helicopters. In such a high strain environment, a random carbon mat material may deteriorate quickly.
Having cruising capabilities of 25,000 ft., i.e. far beyond the envelope of a conventional helicopter, tiltrotor aircrafts must, however, be certified to fly in icing conditions and extreme climates, from Arctic to desert.